US3051207A

US3051207A - Food handling apparatus

Info

Publication number: US3051207A
Authority: US
Inventors: Richard S Hartley
Original assignee: Hobart Manfacturing Co
Current assignee: Hobart Manfacturing Co
Priority date: 1959-10-02
Filing date: 1959-10-02
Publication date: 1962-08-28
Anticipated expiration: 1979-08-28
Also published as: GB955343A; DE1823935U

Description

Aug. 28, 1962 Filed 001:. 2, 1959 R. s. HARTLEY 3,051,207

FOOD HANDLING APPARATUS 3 Sheets-Sheet 1 IN V EN TOR.

RICHARD S. HARTLEY BY ATTORNEYS Aug. 28, 1962 R. s. HARTLEY FOOD HANDLING APPARATUS 5 Sheets-Sheet 2 Filed Oct. 2, 1959 "LIZ 11 111111. f

d 8 m mT M NR 0 W T N ,T I MA D R A H m M R V. B 3 m wfi 3,051,207 FOOD HANDLING APPARATUS Richard S. Hartley, Troy, Ohio, assignor to The Hobart Manufacturing Company, Miami, Ohio, a corporation of Ohio Filed Oct. 2, 1959, Ser. No. 843,993 4 Claims. (Cl. 146-402) This application relates to slicing machines, and particularly to food slicing machines having power driven carriages, and to improved carriage construction particularly adapted to such power drives.

Slicing machines adapted for automatic or semi-automatic operation generally utilize a gravity feed of the material to the slicing blade. In such an arrangement the rotating slicing blade is supported in a plane extending at an angle to vertical, usually an angle of about 45 from vertical, and the carriage may be in the form of a V (in cross-section) with forward and rear walls intersecting at the bottom of the carriage and extending generally at right angles with respect to the slicing plane. Of course, the carriage does not necessarily extend at right angles to the slicing plane, but this is the most usual arrangement. Therefore, the angle at which the material rests within the carriage is sufficient to cause the material to slide downwardly toward the slicing plane, and if a gage wall is provided in front of the knife, then as the carriage is withdrawn on its return stroke from the blade the material will slide into contact with the gage wall, and as the carriage is moved on its forward or slicing stroke the end of the material will engage the knife and a slice will be removed, with the thickness of the slice determined by the setting of the gage wall or plate with respect to the slicing plane.

In order to obtain an optimum slicing capacity the angle of the rearward wall of the carriage, i.e., that wall closest to the knife when the carriage is in its fully forward or fully retracted position, extends at an angle of substantially less than 45 with respect to the plane of movement of the bottom end or edge of the carriage. This permits the material to rest well down in the carriage and to make optimum use of the knife diameter, while still permitting the gravity feed.

The forward wall of the carriage in turn extends at a substantially greater angle with respect to the plane of carriage movement, since it is against this wall that the slicing pressure is exerted. In other words, the forward wall acts to back up the material as the material is engaged by the knife. As seen from the above discussion, best results are obtained with the carriage walls positioned as described, but with power drive used to reciprocate the carriage, and with the carriage reciprocating, for example, in excess of fifty times a minute, the inertia effect upon the material resting freely within the carriage, at the time when the end of the slicing stroke is reached and the carriage abruptly moves back on its return stroke, will cause the material to roll up the rear carriage wall, interfer-ing with the gravity feed, and possibly throwing the material out of the carriage, over the upper end of the rear carriage wall. Clamping the material within the carriage does not provide a satisfactory solution to this situation, since this may well interfere with proper gravity feed of the material.

Accordingly, one of the principal objects of this invention is to provide a slicing machine having a power driven carriage for the material being sliced, and incorporating a fence extending from the rear carriage wall and adjustable toward and away from the forward wall of the carriage, to prevent substantial movement of the material up the surface of the rear wall upon reversal of carriage movement, particularly from the slicing to the return stroke,

2 and without interfering with the gravity feed of the material to the gage wall or plate and slicing mechanism.

A further object of this invention is to provide such a slicing machine wherein a plurality of such fences may be mounted in adjustable spaced relation to each other, for supporting and feeding more than one piece of material on the carriage to the slicing knife.

Furthermore, in many instances it may be desirable to provide for added cariage movement beyond the limits of the power driving mechanism, and to provide for a quick disconnection of the drive connection to the carriage whereby the carriage may be operated manually over an extended stroke. While a number of mechanisms have been proposed for this purpose, for the most part they are quite cumbersome and difiicult both to manufacture and to maintain.

Accordingly, another object of this invention is to provide power drive mechanism for the carriage of a slicing machine which is of essentially simple and economical construction, employs a minimum of moving parts, and is therefore easy to assemble and to maintain.

Another object of this invention is to provide such a power drive mechanism for the carriage of a slicing machine wherein the rates of acceleration and deceleration in change of direction of the carriage are controlled so as to reduce the effect of inertia forces upon material in the carriage.

A further object of the invention is to provide in conjunction with such power drive mechanism a speed control, whereby the speed of the carriage drive may be varied without changing the speed of rotation of the slicing knife.

An additional object of the invention is to provide a power drive for a slicer carriage incorporating easy to operate controls which permit the operator to engage and disengage the power drive readily and quickly.

Other objects and advantages of this invention will be apparent from the following description, the accompanying drawings and the appended claims.

In the drawings- FIG. 1 is a perspective view of a slicing machine embodying the features of the present invention;

FIG. 2 is an enlarged front end view of the slicing machine shown in FIG. 1, with a portion of the cover broken away to show details of the carriage drive mechanism, which are in turn shown partially in section and partially in elevation;

FIG. 3 is a detail view of a portion of the drive mechanism shown in FIG. 2, with parts thereof moved to the engaged position;

FIG. 4 is a view looking inward and down from the upper edge of the carriage as shown in FIG. 1, and showing an additional fence in position on the carriage;

FIG. 5 is a broken sectional view t ken on line 5-5 of FIG. 4;

FIG. 6 is a partial View looking down upon the carriage as shown in FIG. 4, and broken away to show the connection between the adjustable fences and the mounting rail;

FIG. 7 is a somewhat schematic view looking upward, from the bottom of the slicing machine as shown in FIG. 2, showing the layout of the drive mechanism for the carnage;

FIG. 8 is a partial section taken along the line 8-8 in FIG. 7, showing the drive arm in a moved position;

FIG. 9 is an enlarged partial section on line 9-9 of FIG. 8;

FIG. 10 is an enlarged bottom view of the drive mechanism, particularly as shown in FIG. 8, illustrating the carriage speed shift mechanism; and

FIG. 11 is an enlarged detail section of the gear shift mechanism taken on line 1111 of FIG. 10.

Patented Aug. 28, 1962 Referring to the drawings, which show a preferred embodiment of the present invention, the slicing machine includes a housing having a sub-base 16 which is provided with feet 12. The upper portion of the housing includes the main base which extends over the drive mechanism for the rotary slicing knife 20 (FIG. 2 and for the support and drive structure for the carriage 22, which is adapted to reciprocate back and forth with reference to the slicing plane, defined by the cutting edge of knife 20, to feed material to be sliced thereto. The carriage preferably may extend generally at right angles with respect to the slicing plane, which in turn is inclined with respect to vertical, such that the material on the carriage will feed under force of gravity toward the slicing knife.

Forward of the knife 20, at the forward end of the stroke of movement of the carriage, is a gage wall 25. This gage plate may be moved toward and away from the carriage under the control of a knob 27 having a graduated reference dial 28 and suitable connecting linkage, indicated by the general reference numeral 29. This connection may be of the type, for example, shown in U.S. Patent No. 2,573,859, issued to the same assignee as the present application.

Movement of the gage plate with reference to the slicing plane will determine the downward advance of material on the carriage, under force of gravity, as the carriage moves through the forward portion of its reciprocatring stroke, thus determining the thickness of the slice removed from the lowermost portion of the material by the knife. If desired, in order to assure proper gravity feed of the material, this may be augmented by a holder 30 having projections from theforward face thereof and mounted on a sleeve like member 32 which is carried by a rod 33 at the upper forward edge of the front carriage wall 35 (FIG. 2). The construction and operation of holder 30 is essentially known in the art, for example as in U.S. Patent 2,573,861, and forms no part of the present invention per se.

Referring to FIG. 4, the mounting pedestal 36 for the carriage is shown as including V-shaped ways 37 thereon which receive a mounting neck 38 projecting from the undersurface of the rear wall of the carriage. These parts are held in engagement by the thumb screw 41. As will be clear from inspection of FIG. 4, the carriage front wall 35 extend at an angle of approximately, or in excess of, with respect to the path of travel of the carriage, from left to right as viewed in FIG. 4, during movement of the carriage, feeding material to the slicing knife. The rear Wall 40 preferably extends at at least 90 from front wall 35 to provide optimum slicing capacity, and thereforethis wall extends at an angle (with respect to the feeding path of travel) substantially less than the angle of the forward wall 35. In an actual embodiment of the invention the forward wall 35 extends at approximately 60 from the path of travel, and the rear wall extends at approximately 30, with the included angle therebetween being 90". a

This arrangement of the carriage walls, as noted previously, provides. optimum slicing capacity, since the forward edge of the material 42, shown in dot-dash lines in FIG. 4, is relatively low with respect to the rotating knife during its approach thereto. During hand operation of the carriage, this arrangement has no particular effect upon the slicing operation, since the return movement of the carriage can be regulated accordingly by the operator. However, when the. carriage is reciprocated by a power drive, particularly where it is desired to have a power drive of the simplest possible construction, for reasons of construction expense and maintenance, then the. low slope of the rear'carriage wall 40 may provide difficulty for the reason that on a returnstroke of substantially equal speed, and more particularly during the rapid change of acceleration at the end of the feed stroke and beginning of the return stroke of the carriage, the inertia efiects on the material may cause it to slide or roll (in the case of round objects) up the rear wall and perhaps be turned within the carriage. For this reason it is desirable to provide a barrier which will prevent the material from undesired movement within the carriage, but which will not interfere with the gravity feed of the material.

Therefore, in accordance with the invention a fence member 45 is provided which extends transversely of the carriage rear wall, and projects substantially perpendicnlar to the surface thereof, carried by an integral arm- 47. This arm terminates in a C-cl-amp arrangement having at one end thereof beveled surfaces 52 which engage complementary bevel surfaces on a way or rail 53 formed along the bottom of rear carriage wall 40, extending from front to back thereof. A holding screw 54, having a knurled head 55 for easy adjustment, is threaded into the clamp structure for engagement with the opposite side of the rail 53 from the interengaging bevel surfaces, to clamp the fence in any desired position along the surface of carriage wall 40.

The fence member 45 also is provided with substantially flat front and rear walls, as can be seen most clearly with reference to the segment of the fence shown in FIG. 6, and the free end of the fence projects substantially to the lower edge of the carriage as shown in FIG. 5. Under some circumstances it may be desirable to slice more than one loaf or piece of material at the same time, and therefore it is possible to utilize a plurality of such fence members, as shown in FIGS. 4 and 6-, with the back face of the lowermost fence 45 acting in lieu of the front wall 35 of the carriage to support the rearwardmost piece of material for gravity feed toward the slicing knife. Other parts of the second fence are likewise indicated with the same reference numerals as the fence 45, but with a prime added.

As will be clear from inspection of FIG. 4, the

fences

45 and 45 may be adjusted with reference to material on the carriage so as to leave a slight space 57 between the front face of each fence and the material. During most of the slicing operation there is no direct contact between the material and the fence, but during the change of direction of the carriage, particularly under power feed, the material may slide slightly upthe surface of rear wall 40 and will then engage the fence, being thus prevented from substantial movement on the carriage during the change in direction.

The present invention also includes a novel simplified power drive for the carriage which includes provision for driving the carriage at different speeds while driving the rotary slicing knife at the same speed, preferably from a common drive motor. Referring again to FIG. 2, the knife 20 is mounted upon an arbor 60 whichrotates in bearings 62, and which is driven by a worm gear 64 secured to the lower end thereof and driven by a worm drive 65 carried on the output shaft 66 of the drive motor (not shown), which is enclosed within the upper housing 15. a a

Worm drive 65 also meshes with a worm gear 70 (FIGS. 2, 8 and 9) fastened to the upper end of a drive input shaft 72. This shaft is mounted inbearing 73 within a sleeve 74 bolted to a drive subassembly unit 75, which in turn is bolted to the underside of the housing 15. The lower end of drive shaft 72 has a pair of input pinions formed thereon, the upper pinion 76 being larger and the lower pinion 77 smaller, and the lower end of this shaft is secured to one gear 78 of a conventional meshing. gear type positive displacement pump, having J Qther gear 79, and enclosed within a cavity 80 at the bottom of the subassembly unit by a cover 82. The output of this gear pump is through a tube extending upwardly .toward the worm gear 70, and terminating immediately therebelow such as when the shaft is rotated, lubricant is pumped out of tube '85 and sprayed-against worm gear 70, and thereby carried about to the inputgworm 65 to lubricate it, as well as the knife drive worm 64. The interior of the subassembly 75 provides a well within which the lubricant, for example oil, is carried, and which is connected to the input of the pump through a suitable passage (not shown).

A countershaft 90 is secured at its lower end to an output crank 92 by a cross pin 93, and extends upwardly within the subassembly unit 75 parallel to and spaced from the input shaft 72. Preferably, a seal 94 (FIG. 11) surrounds the shaft immediately above its bottom, and directly below a roller bearing 95. A first output gear 97 is carried in free rotating relation upon shaft 90, resting upon a thrust Washer 98. Immediately above this gear is another washer 99 upon which rests the second output gear 100, which also is freely rotatable on countershaft 90.

Each of these gears includes a keyway, 101 and 102, respectively, and a movable key 105 is slidably received Within a slot 106 extending in the upper end of countershaft 90. The key is normally biased by spring 108 to engage with one or the other of the

keyways

101 and 102, moving over the inner edge of washer 99, which causes the key to dive into the keyways. Movement of the key axially within slot 106 is provided by a collar 1 to which one end of the key is pivotally secured, and which in turn is engaged by studs 112 on opposite ends of a shifting fork 115 which is keyed to a shaft 117 extending over the top of the output gears. One end of shaft 117 carries an arm 120 to which is fastened a shift rod 122. This rod carries a collar 123 fixed thereto and fastened at one end to a spring 124 which is hooked at its other end over the edge of cross shaft 117.

The shift rod 122 extends forwardly through the base of the machine and projects through the front wall thereof, terminating with an operating knob 125 outside the front of the base. Thus, spring 124 normally biases the shifting mechanism in a direction to position key 105 in the keyway 101, engaging the lower speed output gears 77, 97 with the crank 92. Then, if the operator pulls outwardly and upwardly upon knob 125 the key 105 will shift into keyway 102 and the drive will be at a higher speed through

gears

76, 100, in which position the shift rod 122 may be retained, for example, by engaging a notch therein (not shown) with the edge of the aperture in base 10 through which it extends. The operator may then release the high speed carriage drive merely by touching the knob 125 to disengage the rod 122, and it will be drawn .to its low speed position by spring 124.

The output crank 92, therefore, rotates continuously .when the slicing machine is operating, at one of two speeds as determined by manipulation of the shift rod.

This crank is pivotally connected through a pin 130 to a connecting rod or link 132 which is in turn pivotally connected through a pin 134 at its other end to the driven end of an oscillating carriage drive arm 135. This arm is fixed to a shaft 137 which is rotatably mounted in bearings 138 in the subassembly 75, and the other end .of arm 135 projects beneath the path of movement of the carriage, and has an upwardly extending sleeve 140 secured thereto. Within sleeve 140 is a pin 142 having a slot 143 receiving the end of a set screw 144 which is threaded through the wall of the sleeve. The upper end of pin 142 carries a roller 145, preferably formed of nylon or similar relatively hard plastic material, and having a beveled edge 146. The pin is normally biased by a spring 148 beneath its lower end to a raised position, substantially as shown in FIG. 2, but is capable of being lowered against this spring upon exertion of pressure against the beveled edge 146.

Therefore, rotation of-output crank 92 causes an oscillating movement from the drive arm 135, and the geometry ofthe system causes the roller 145 to subscribe an arc, the end positions of which are shown by the dot-dash lines 150 in FIG: 7.- In passing through this are the roller at thesame timemoves laterally with reference to the linear path of-movement of the carriage, the limits of this movement being illustrated by the full line and dotted line positions of the roller as shown in FIG. 2.

The mounting pedestal or carriage tray support 36 extends around the outside of the portion of housing 15 which covers the gage plate control, as shown particularly in FIG. 2, and then inward through an opening 152 in the side of the housing, terminating in a horizontally extending carriage bearing 155 which is mounted on a carriage support shaft 160. This shaft extends fore and aft of the housing, and is mounted in stationary position by any suitable means at its opposite ends, for example as shown schematically at 161 in FIG. 7. A further shaft 162 extends parallel to shaft and carries a sliding sleeve member 163 which is connected to the carriage pedestal through an adjustable connection 164, as shown in greater detail in said Patent 2,573,861. A handle 165 is mounted on the pedestal, extending upwardly of the front wall 35 of the carriage for manual operation thereof.

Referring specifically to FIGS. 2 and 3, the carriage pedestal includes a releasable connection for engagement with the drive roller 145. This connection is provided by a stationary sleeve secured thereto and having a vertically slidable pin 172 received therein, including a central undercut portion 173 (FIG. 3). A stop pin 174 extends through the wall of sleeve 170 and into the areas of the undercut to limit the vertical movement of the sliding pin 172.

At its lower end pin 172 carries a track member 175 having a transversely extending channel 176 formed in the undersurface thereof, and of sufiicient width to receive the roller 145. This track member is normally biased upward to where it is above the level at which the roller 145 moves, as shown in FIG. 2. The biasing force is provided by a spring 178 secured at opposite ends to a stationary point on the carriage pedestal and to the track member 175.

An engaging lever 180 is pivoted on the tray support at 182 and its inward end extends into a slot in the head or top of the sliding pin 172. The end of lever 180 includes a slot 183 through which a pin 184 extends to provide for a drive connection between the lever and the track carrying pin 172. The other end of lever 180 is provided with a handle 185 at its end, and somewhat inwardly thereof, toward the pivot 182, a laterally projecting lug 137. Generally above this lug, and handle portion 185, is an operating latch in the form of a bell crank pivotally mounted at 192 upon the tray support adjacent the carriage bearing, and having a generally vertically extending operating or handle portion 193. The other end of the bell crank is provided with a hook-like projection 195 engageable beneath lug 187 when the lever 180 is pivoted in a counterclockwise direction, as viewed in FIGS. 2 and 3, to lower the track member 175.

The power drive to the carriage may thus be engaged as follows. Assuming that the motor is deenergized and that the knife and drive arm 135 are stationary, the operator pulls up upon the handle portion 185 of lever 180, and this drives the track carrying pin 172 downward against the bias of spring 178. The latch bell crank 190 falls, by force of gravity, in a clockwise direction about its pivot so that the hook portion 195 engages beneath lug 187 to hold the parts in the engaged position as shown in FIG. 3. The operator may then grasp the carriage handle 165 and reciprocate the carriage until the depressed track member 175 engages the roller 145, which will cam under the track member by reason of its beveled edge 146 and spring bias 148, to engage within the cross slot or channel 176. The operator may then begin automatic slicing operations by actuating switch 198 (FIG. 1) which energizes the drive motor in the usual manner to rotate the knife and oscillate the drive arm 135 through the drive connections as previously described.

The roller 145, in moving through the limits of its arcuate movement, will roll back and forth within the track slot 176, as shown by comparison of the full line and dotted positions in FIG. 7, and drive the carriage in the 7 linear path as defined by its supporting rod 160, along which the pedestal 3,6 slides.

By mounting the track channel 176 as a part of the carriage hearing, which moves in a linear direction, and by having the roller 145 mounted for movement in an arc on the drive arm 135, the geometry of the carriage drive system is such that the deceleration and following acceleration of the carriage is proportional to the linear velocity of the roller multiplied by the cosine of its angular position relative to the direction of motion of the carriage.

The speed of reciprocation of the carriage may be al tered by appropriate manipulation of the shift rod 12 between fast and slow positions. At the end of the feed or slicing stroke, when the carriage undergoes a fairly rapid deceleration, if the material being sliced tends by reason of inertia forces to slide off over the rear wall 40 of the carriage, it will engage the fence 45 which is normally spaced slightly therefrom to avoid interference with gravity feed of the material down the carriage, and the material will be retained in proper position on the carriage during the return stroke. As the carriage again undergoes a fairly rapid change in direction at the end of the return stroke, the inertia forces will be such as to move the material 42 toward the front carriage Wall 35, and the material will then slide down the carriage, contacting the corrugated surfaces of the carriage wall as shown in FIG. 4, until the lower end thereof contacts the gage plate 25 as the carriage moves through its feed stroke to force the material past the rotating knife.

If it is desired to operate the carriage manually, an extended stroke may be obtained, since the limits of arm 135 cause carriage movement of less than the full length of rod 160 (see FIG. 7). In a preferred construction, the operator merely taps the handle part 193. of the latch bell crank, releasing the hook portion 195 from lug 187, and the spring 178 will Withdraw track member 175 to its raised position, breaking the drive connection, and upon further energizing of the drive motor the drive arm 135 and roller 145 will merely reciprocate freely beneath the carriage pedestal, while the latter may be manipulated by the handle 165.

While the form of apparatus herein described constitutes a preferred embodiment of the invention, it is to 7 which is defined in the appended claims.

What is claimed is:

1. In a slicing machine having a rotating slicing knife mounted in an inclined slicing plane, an open top carriage extending in an oppositely inclined direction intersecting said slicing plane for gravity feed of material down said carriage to said knife, means mounting said carriage for linear movement parallel to said slicing plane to carry the material back and forth across the cutting edge of said knife, drive means for-power reciprocation of said carriage'including a pivotally mounted drive arm having one end extending generally beneath the path of movement of said carriage, a first drive member supported on said one end of said arm, a second drive member extending from said carriage, roller means mounted on one of said drive members and extending toward the other said drive memher, a track member carried by the other said drive memher. and extending transversely to the direction of movement of said carriage, said track member having sufiicient length to contain said roller during a complete arcuate movement of said first drive member, means connected to move said second drive member selectively into position for driving engagement between said roller and said track to control the drive connection between said carriage and said drive means, and means for retaining said second drive member in a position where driving engagement between said roller and said track cannot be effected.

2. In a slicing machine having a rotating slicing knife mounted in an inclined slicing plane, an open top carriage extending in an oppositely inclined direction intersecting said slicing plane for gravity feed of material down said carriage to said knife, means mounting said carriage for linear movement parallel to said slicing plane to carry the material back and forth across the cutting edge of said knife, drive means for powered reciprocation of said carriage including a pivotally mounted drive arm having one end extending generally beneath said carriage and movable in an arcuate path therebeneath, a roller mounted on said one end of said arm on an axis generally normal to said arm, a track member movably mounted on said carriage and extending transversely to the direction of movement thereof, said track member having sufficient length to contain said roller during a complete arcuate movement thereof, and means connected to retain said track member selectively into and out of position for driving engagement with said roller to control the drive connection of said carriage with its drive means.

3. In a slicing machine the combination of a carriage for supporting material to be sliced, a mounting pedestal for said carriage, means supporting said pedestal for movement along a linear path in a feeding stroke and a return stroke, a swinging drive arm having an end extending beneath said tlinear path and movable in an are generally contiguous with said path, a driver on said end of said arm normally biased to a raised position, a track member supported on said pedestal for movement between a disengaged position and an engaging position intersecting the path of movement of said driver, said track member including a driver receiving channel extending transversely to the linear path of motion of said pedestal, means for latching said track member in the engaging position providing for depression of said driver against its bias and reception thereof within said channel upon contact between said driver and said track member, and drive means connected to said arm for moving said driver through an arcuate path having limits of movement transversely of said pedestal supporting means within the length of said channel.

4. In a slicing machine the combination of a carriage for supporting material to be sliced, a mounting pedestal for said carriage, means supporting said pedestal for movement along a linear path in a feeding stroke and a return stroke, a swinging drive arm having an end extending beneath said linear path and movable in an arc generally contiguous with said path, a driver on said end of said arm normally biased to a raised position, a track member supported on said pedestal for movement between a disengaged position and 'an engaging position intersecting the path of movement of said driver, said track member including a driver receiving channel extending transversely to the linear path of motion of said pedestal, means for latching said track member in the engaging position providing for depression of said driver against its bias and reception thereof within said channel upon contact between said driver and said track member, drive means connected to said arm for moving said driver through an arcuate path having limits of movement transversely of: said pedestal supporting means within the length of said channel, and means for varying the speed of motion of said arm including a control operable from the exterior of said machine.

References Cited in the file of this patent UNITED STATES PATENTS 1,687,072 Van Berkel Oct. 9, 1928 1,824,949 Folk Sept.v 29, 1931 2,177,474 Campbell Oct. 24, 1939 2,456,369 Brustowsky Dec. 14, 1948 2,573,861 Meeker et -al Nov. 6, H951 2,598,740 Zimmermann June 3, 1952 2,822,011 Lundell Feb. 4, 1958 2,912,026 Scharfen Nov. 10, 1959